#!/bin/bash
# Program:
# Try to calculate 1+2+...+${your_input} 
# History:
# 2015-12-22	Puma	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

read -p "Please input a number, I will count for 1+2+...+your_input: " nu

s=0
for ((i=1; i<=$nu; i=i+1))
do
  s=$(($s+$i))
done
echo "The result of '1+2+...+$nu' is ==> $s"
